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Found 46 results

  1. I hope the title is clear enough, essentially what I am trying to do is create a custom image plane that will output an rgb matte for objects being refracted by another object. (in my case objects inside a glass sphere) lets say i give an object inside the glass sphere a vector attribute of green {0,1,0} is it possible to output an image plane that displays that attribute through the refraction of the outer sphere? I've been searching for a while all over google and OD but have yet to find exactly what I'm after.. I feel like Trace() is about the closest thing I could find, but not sure how that would work for what I'm trying to accomplish.. Perhaps my approach is wrong as well, if anyone knows hows to accomplish something like this, I'm all ears. Ideally I'd like to accomplish this with image planes if possible and avoid having to create separate takes and what not.. Thanks!, -C
  2. Access "dead" attribute in a point

    I was reading some comments on how the @dead attribute generated by particle streams changes to 1 in the subframe before being reaped by the solver. Is there anyway to access this attribute after the simulation? For example, if I wanted to create a static point in that same position as the particle that is going to die? By the way, the generated particles are not from a POP Network, but yes from a FLIP simulation.
  3. As I can understand from the Houdini documentation, the "@opinputn_name" will access attributes from the secondary inputs. I am trying to access the "numpt" by "int numLastPoint = i@opinput1_numpt;" but this does not work. Im I missing something?
  4. Help with the Cube Man

    Hey Guys, I am working on making a character out of cubes. Basically I want to be able to have the cubes on the mesh, conform to the topology and then have the control to be able to move, rotate and scale the cubes independantly while still conforming to the mesh. I have been looking around and found some good solutions for this (see attached images 1 and 2) and I feel that I am close but I have been running into a few snags that seem to be a bit above my level of expertise and was hoping to get some assistance. As you can see in image1 the rotations seem to tear or collapse into the cubes as opposed to rotating on a local axis from where it is placed. Basically after calls to primuv and prim_normal any calls to rotate or scale points don't seem to apply the way they should or how you would expect them to. (I hope that makes sense.). If you guys see or know of a better way to implement this type of solution then I would be more than happy to listen and learn. Thanks for your time. Cheers, Christian
  5. Find Adjacent Faces

    Hi, For a tool I've been working on, I need to have a way of finding adjacent faces between the inside of fractured pieces. I want to store this as a primitive attribute, that gives the number of the adjacent primitive. The way I have done it is by calculating the centroid of each primitive (using getbbox_center) and then iterating through the primitives in a for-each loop, finding the other primitive with the same centroid. (it turned out that the centroids were different by a tiny amount, so I introduced an accuracy value that you can set, and it finds the adjacent primitive within that distance). It then stores this as a primitive attribute. All seems to be working fine on simple fractures, but as soon as you sent the number of fractures higher than 22, it seems to bug out and all the adjacent faces are incorrect. I have visualized this in the HIP file by having a subnet that draws lines between adjacent faces. Attached is my HIP file. If anyone has any idea what could be causing this issue, I would be very grateful! I have also noticed that it seems to be a bit slow to calculate the adjacent faces, so if anyone knows a more efficient way of doing this, I'd also be pleased to hear it. Best, Stephen FindingAdjacentFace.hipnc
  6. Freezing Attributes

    Hi Odforce! Im working on a little project using the object packing technique from Ben Watts Design's tutorial. I've got an attribute VOP using turbulent noise to drive the pscale attribute. Im then reading this into a popnet through a sop solver, but when the particles move they adopt the pscale of the underlying position of the noise. I believe this issue is related to the sop solver reading the new pscale in every frame but im unsure how to essentially freeze this attribute. I want the points to be born, adopt the pscale based on the location it spawns on, then for the pscale attribute to remain frozen for the rest of the simulation, how do i go about setting this up? I have attached the scene file here. CardGrowth.hip
  7. I am trying to get some temperature data that I have calculated on the output of a particle simulation to make it work with the pyro shader, but I can't seem to get it to transfer. I am using Volume Rasterize Points to get the particles into being a volume, which is working really well, but I can't seem to get anything but the density field filled. The node supposedly takes point attributes and fills a volume field with the data if it exists as both a field and a point attribute, which these do, but I keep coming up with empty fields. Failing that, I tried to brute force them over using Volume from Attribute, which I had successfully used elsewhere in the scene, but to no avail. Still giving me empty fields. This has started to become quite vexing, as I think it should be working how I have it setup, and it isn't. particleTest1.hip
  8. If backbone is poly, attributes come across to geometry created by sweep If they are nurb, resulting geometry gets '0'.. wondering if that's a bug, or expected.. thanks Alex help doesnt mention backbone nurb vs poly.. These point attributes and groups will be copied from the backbone points to the cross-section points. If a uv attribute is present on both the cross-section and backbone, and Cycle Type is set to either One Primitive at a Time or Cycle Primitives, only the u component will be copied from the backbone, so the v component will still be from the cross-section uv attribute. Although only point attributes are copied from the backbone, there is a special case for if the cross-section has a vertex uv attribute, point uv values can be copied into the destination vertex uv attribute, but this only works for uv.
  9. I feel like Houdini must be able to do this, but I can't figure it out... I want to take a vector point attribute and write it out to a 16-bit image file. So for example, for point 0, my attribute @out_P has a value of {561.0, 981.0 ,1174.0 }. I want to create an image sized 256x256 pixels and write the first pixel value to be this value of @out_P. Second pixel is the @out_P value of point 1, and so on... How would I go about doing this?
  10. hi there, I have a global attribute that i've made in a python node: citySearcherDistanceTrav = geo.addAttrib(hou.attribType.Global, 'citySearcherDistanceTrav', '') i've then set the attribute with some floats totalDistance = self.stepSize * hou.frame() #speed * time = distance travelled dt = str(totalDistance) geo.setGlobalAttribValue('citySearcherDistanceTrav',dt) #see image 1 But i can't seem to access the values in the next node directly below. I tried find global attrib not sure how to access the data in a python node again. A
  11. Hi, I've tried it over and over. Suddenly the complete attributes are missing in the POP. I dont know the concrete circumstances when it happens. I think its different. Is it my fault, missing something, a bug? disintegration_v.2.hip
  12. Hi, I've tried it over and over. Suddenly the complete attributes are missing in the POP. I dont know the concrete circumstances when it happens. I think its different.
  13. Hi, I've tried it over and over. Suddenly the complete attributes are missing in the POP. I dont know the concrete circumstances when it happens. I think its different. disintegration_v.2.hip
  14. Hello, one question please: What expression can I write to use the @ptnum attribute to drive the @P.y attribute using VEX or Python expressions. What if I want to drive @P.y with @P.x ?? thanks in advance.......
  15. use of Energy Attribute - FEM

    Hey guys, About this energy attribute, I think I could make a good use of it but I don't know how to access it. I mean, I can see it in the dops geometry spreadsheet but it doesn't get out there. I can't see it in sops. My main doubts are: - Can I bring this attributes to sops? (dissipationdensity, kineticdensity, potentialdensity) - Can I use it in dops? (use it as a multiplier for some other parameter, like the fracture threshold for example) Thank you fem.energy.v1a.rar
  16. Hi there, I am trying to build a propagation driven blend / morph effect to change the look of a geometry. But I am already stuck by transfering the atrributes between the geo A and geo B. I managed to build a set up where I change the geometry by using a attribute vop and subtracting B minus A. Here come the BUTs couldn´t animate it by keyframing the Bias of a mix node. couldn´t use a propagation effect with scattert points In the second set up I tried to change the set up by using a scatter node insted of the normal geometry. It works but it seems that the point order isn´t the same and while changing the bias of the mix node all the points change it´s position?! In the scatter node I unchecked "Rondomize Point Order" but without any effect. I also tried to use set up with the change from lowres mesh to a highres mesh, but here I couldn´t get solution with the scattered point, because of the primitive Attribute node in the second Vop. I also tried to recreate it with point cloud node but failed as always. I am pretty new to Houdini and I know that I am missing a lot of foundation knowledge, it would be great if someone could give me a hint what I am doing wrong. Thanks and all the best Dennis 170422_position_transfer_001.hiplc
  17. Deleting wet attribute

    Hi, probably a simple one but I'm having problems deleting points based on a point attribute called "wet". So its a wet map. The delete sop isn't willing to delete anything here. Any hint? Thanks
  18. Group Attribute

    Looking at the Geometry Spreadsheet. A Group SOP creates an attribute like "group:foo": I can easily access that group "attribute" in a Wrangle like so: i@myvalue = @group_foo; QUESTION: How do I access that group attribute on parameters that requires an attribute name? For example, in a Color SOP's Random from Attribute: Or on a Delete SOP's Filter Expression: Although I know that I could just type the group name on the group field. I'm just curious if there's a way to access the Groups data as "Attributes". Particularly, I'm asking because I want to access Groups as an "Attribute" in the Enable Solver DOP without actually creating an actual attribute to represent the group: Hopefully I'm just missing or forgetting the proper syntax.. P.S. The Enable Solver could use an option where it can check for existing groups. I'll probably send an RFE
  19. POPS

    Hi all, I am trying to use geometry to control attributes on particles. Would anyone know how to do that? Problem. I have a flat bed of sand grains with their "static Kinetic" set very high. But I would like the collision geometry (a hand in this case) to diminish the "static Kinetic" attribute to a very low setting. Much like using the sop solver for fluids. Cheers, dreamagery
  20. Temporary variables in VEX Help

    Hi I'm new to this wrangle node programming, I've been busting my head over why this doesn't work for three days, it's so simple therefor i must be missing out on some general vex concepts. If anyone can please point me in the right direction that would be greatly appritiated. I have a bunch of points on a grid and their moving up and down via noise. I am trying to set up a point attribute that has a value of 1 when a point if moving up (positivly in the Y axis) and a value of 0 when a point is moving down (negativly in the Y axis). This attribute is called Direction, I'm computing the logic on temporary VEX variables and then writing them out to the attributes. Here's how it looks like : // 0 is going down, 1 is going up, -1 means the point has no direction // on the first frame they have no direction so the points just take their current heights so they can use them for comparison on the second and every other frame int temporary_Direction; float temporary_Previous_Frame_Height; if(@Frame == 1) { temporary_Direction = -1; temporary_Previous_Frame_Height = @P.y; } else { temporary_Direction = @Direction; // ------------> this is where the problem is (this is here so that the temporary variable get's the value of the currently proccesing point every frame) temporary_Previous_Frame_Height = @P.y; if(temporary_Direction == -1) // If the point has no direction { if(temporary_Previous_Frame_Height < v@P.y) // If it's going up { temporary_Direction = 1; temporary_Previous_Frame_Height = v@P.y; } if(temporary_Previous_Frame_Height > v@P.y) // If it's going down { temporary_Direction = 0; temporary_Previous_Frame_Height = v@P.y; } } } // Out_Values i@Direction = temporary_Direction; f@Previous_Frame_Height = temporary_Previous_Frame_Height; // Out_Values The problem here seems to be when I declare "temporary_Direction = @Direction", for some reason on the second frame when I read @Direction the value wich is given to temporary_Direction is 0 instead of -1 wich was given to every @Direction on the first frame. Temporary_Previous_Frame_Height updates just fine but temporary_Direction doesnt. Also writing "if(temporary_Direction == -1)" doesnt seem to work either. Is my thought process even slightly right here, what am i doing wrong, are temporary variables created in vex something that exist globally and in order to use them per point we need to read each point's values or are temporary variables something that exist for every point. Also why do i have to give values to all attributes every single frame or else they will reset to 0 (hense the Out_Values section). //////////////////////////// Update Thank you everyone for replying. I've tried out the time shift sop and it work's fine now( I dont even need the Previous_Frame_Height attribute anymore). I've updated the main post with the original hip file and the one with the time shift sop. Learning about the time shift sop is great, but i would still like to improve my thought process on writing code. It would be greatly appritiated if someone can take a look at the original hip file and possibly shed some light on the problem. I've added notes inside the original hip file for clarity. Any help would be appritiated Thanks in advance Original.hip Time-Shift SOP.hip
  21. hey guys i'm trying to do a basic FEM test here and having a prob with attributes I paint up an attribute call 'shapestiffness' then i'm trying to pass that to dops - so i've entered @shapestiffness into the slot in the solid object node in my dop network. My understanding is that the attribute should act as a multiplier but i cant get it to work it just splats on the floor this is probably comically easy for some of you but i'm still trying to wrap my head around attributes to control objects and stuff so bear with me I've attached a super simple ball scene where you can prob see what i'm failing to do lol! anyone got a few mins to take a quick look? ta ant shapestiffness_variable_FEM_test01.hip
  22. Like the title says. I'm trying to kind of make my way through the SHOP context, but my biggest problem is accessing information from the actual geo. I made a fairly simple scene where I am running a sin over the sphere's @pscale. In this case I'm just trying to have the @pscale control the principal shader's emission amount. I tried making an attribute VOP where I bind the @pscale to a bind export and then named it "lit". After this point I can't fin an answer online how to access and connect that attribute to the emission. I know it has to be the easiest and most obvious node, but I can't seem to find the answer. All help is much appreciated! size_lit.hipnc
  23. What is the difference between creating the name attribute in the voronoi fracture, or later in the assemble?
  24. FumeFX VDB in Houdini?

    So I come from a Max background using Vray. I can load in VDB's from Houdini through Vray's VolumeGrid. I was trying to do the reverse; load in FumeFx VDB's into Houdini. I can load in the VDB's no problem and I see it in the viewport. However, trying to use the volume shader is entirely different. When I click the VDB in the viewport and go to the primitives view I can see Fume's channels. I'm not sure it's even possible but I attached a screenshot to better explain what I'm talking about. I would attach a .VDB file but it's 100mb so...But the scene is literally loading in the file and then has a transform to scale it down. Thanks!!!
  25. Student Demo Reel

    Back in January I didn't know Houdini existed until I started school and ever since I've been trying to learn as much as I can. I still have a lot of work to do and there is a lot more I want to learn/try but this is all I've learned up until now.
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